When producing square beams with or without rough edges, it is important for the side surfaces of the square beam to be produced parallel to the lengthwise or middle axis of the tree trunk, since this is important both for the structure and strength of the square beam and also with respect to the cut rough edges when they are processed further for example into small parts (laths). It is therefore important for the tree trunks to be positioned in the same location of the lengthwise axis as much as possible parallel to the direction of motion in which a holding device for the tree trunk and the tools are moved relative to one another in order to minimize the adjustment effort for the holding device and the tools. This however results in the holding device grasping the tree trunks with always the same location of the lengthwise axis.
AT 397 058 B discloses a device of the initially mentioned type which has a means for positioning the tree trunk which is opened during working and the tree trunk is held on the end face during working. If with the known device square beams are to be produced, the tree trunk must be turned 90.degree. after working the two first sides which are opposite one another. Here it is disadvantageous that the tree trunk was originally not grasped in the middle, since based on its conical shape it was positioned with a lengthwise axis which is oblique in the vertical direction. The tree trunk must therefore be positioned again after turning and must be grasped by the holding device so that the other two sides of the tree trunk can also be worked parallel to the lengthwise axis.
EP 222 728 A and EP 217 784 A disclose devices for producing square beams which grasp the tree trunk such that the location of its lengthwise axis viewed in the horizonal direction is always aligned the same. The height of the lengthwise axis of the individual tree trunks or their alignment in the vertical plane however, depending on the diameter of the tree trunk, is not always fixed exactly the same. Furthermore the holding devices described there on the same page are the means for positioning the tree trunks, i.e. there are no additional system parts which position the tree trunk before grasping by the holding device in which it is held during working.